Klaus Winter

NaCl-induzierter crassulaceensäurestoffwechsel bei Mesembryanthemum crystallinum

Summary Mesembryanthemum crystallinum grown under saline conditions in NaCl medium shows the typical gas exchange reactions known from CAM plants, exhibiting a clear CO 2 uptake in the dark. This is accompanied by an increase of malate content in the leaves. Neither CO 2 uptake in the dark nor increase in malate content is found in plants grown in the absence of NaCl. These results, suggesting a drastic metabolic change caused by NaCl, are discussed.

Seasonal shift from C3 photosynthesis to Crassulacean Acid Metabolism in Mesembryanthemum crystallinum growing in its natural environment

SummaryChanges in δ13C value, diurnal malate content, water content and Na+, K+ and Cl- content of the annual Mesembryanthemum crystallinum (Aizoaceae) were followed in a natural population on a coastal cliff at the Mediterranean Sea shore close to Caesarea (Israel). Plants germinated in the middle of the rainy season in December 1976/January 1977. Diurnal malate fluctuations in the leaves were not detected until the end of March. Later on, at the start of the dry season, pronounced diurnal changes in malate developed. This was correlated with a progressive change in δ 13C value from about -26‰ to about -16‰ which is consistent with a change from normal C3 photosynthetic CO2 fixation to a predominantly nocturnal CO2 assimilation pattern involving Crassulacean Acid Metabolism.

CO2-Fixierungsreaktionen bei der Salzpflanze Mesembryanthemum crystallinum unter variierten Außenbedingungen

The correlation of CO2-fixation metabolism to various environmental conditions such as NaCl content of culture medium, air humidity and light intensity was investigated in the halophytic species Mesembryanthemum crystallinum. The data obtained demonstrate that a change in photosynthesis from C3-pathway to crassulacean acid metabolism (CAM) is observed not only in NaCl treated plants as reported earlier but also in control plants grown in non-saline medium when environmental conditions (high light intensity, low air humidity) cause a water deficit in the leaves. It is suggested that water stress plays an important role in regulation between C3- and CAM-pathway of photosynthesis in Mesembryanthemum crystallinum.SummaryThe correlation of CO2-fixation metabolism to various environmental conditions such as NaCl content of culture medium, air humidity and light intensity was investigated in the halophytic species Mesembryanthemum crystallinum. The data obtained demonstrate that a change in photosynthesis from C3-pathway to crassulacean acid metabolism (CAM) is observed not only in NaCl treated plants as reported earlier but also in control plants grown in non-saline medium when environmental conditions (high light intensity, low air humidity) cause a water deficit in the leaves. It is suggested that water stress plays an important role in regulation between C3- and CAM-pathway of photosynthesis in Mesembryanthemum crystallinum.

Zum Problem der Ausbildung des Crassulaceensäurestoffwechsels bei Mesembryanthemum crystallinum unter NaCl-Einfluß

SummaryMesembryanthemum crystallinum plants were grown for 10 weeks in soil culture and, during the final 3 weeks, watered with NaCl solutions varying in concentration between 50 and 500 mM. Plants show an increasingly less negative net CO2 balance and increased malate accumulation in the leaves during the dark with increasing NaCl concentration. There is a positive net CO2 balance above 100 mM with a maximum at 350 mM NaCl. Plants watered with 350 mM NaCl do not display this characteristic feature of crassulacean acid metabolism (CAM) initially, i.e. during the first week after the commencement of NaCl treatment. However, after this adaption period net CO2 balance during the dark begins to approach a positive value. Malate accumulation in the leaves during the dark increases rapidly after the first week of NaCl treatment, reaching a constant level after about 3 weeks. Leaves which develop after commencement of NaCl treatment produce less malate during the dark than leaves which were already present at the onset of NaCl watering. Na+ content in the leaves is higher than Cl- content when plants are watered with NaCl solutions. Four-and-a-half-month-old plants grown under soil culture without addition of NaCl also exhibit CAM, probably because of ion uptake from the soil which causes increase in Na+ and Cl- contents in the leaves. Na2SO4, KCl and K2SO4 have effects similar to those of NaCl on gas exchange reactions of Mesembryanthemum crystallinum.Mesembryanthemum crystallinum plants were grown for 10 weeks in soil culture and, during the final 3 weeks, watered with NaCl solutions varying in concentration between 50 and 500 mM. Plants show an increasingly less negative net CO2 balance and increased malate accumulation in the leaves during the dark with increasing NaCl concentration. There is a positive net CO2 balance above 100 mM with a maximum at 350 mM NaCl. Plants watered with 350 mM NaCl do not display this characteristic feature of crassulacean acid metabolism (CAM) initially, i.e. during the first week after the commencement of NaCl treatment. However, after this adaption period net CO2 balance during the dark begins to approach a positive value. Malate accumulation in the leaves during the dark increases rapidly after the first week of NaCl treatment, reaching a constant level after about 3 weeks. Leaves which develop after commencement of NaCl treatment produce less malate during the dark than leaves which were already present at the onset of NaCl watering. Na(+) content in the leaves is higher than Cl(-) content when plants are watered with NaCl solutions. Four-and-a-half-month-old plants grown under soil culture without addition of NaCl also exhibit CAM, probably because of ion uptake from the soil which causes increase in Na(+) and Cl(-) contents in the leaves. Na2SO4, KCl and K2SO4 have effects similar to those of NaCl on gas exchange reactions of Mesembryanthemum crystallinum.

δ13C values of grass species collected in the northern Sahara desert

Summaryδ13C values were measured for 45 Poaceae species collected in the northern Sahara desert, at the foot of the Saharan Atlas. The results indicate a clear relationship between carbon isotope discrimination and phytogeographical distribution of the grasses. Mediterranean species predominantly had δ13C values indicating the C3 pathway of photosynthesis. By contrast, nearly all species belonging to the Saharo-Arabian and /or Sudanian group showed a C4 like carbon isotope composition. Leaf material of two species, Lygeum spartum and Stipa tenacissima, had δ13C values in the region of-20‰, i.e. intermediate between the mean δ13C values of C3 and C4 plants. However, additional speciments of both these grasses obtained from a different source (herbarium of the Hebrew University, Jerusalem) yielded a C3 like carbon isotope composition.

Evidence for the significance of crassulacean acid metabolism as an adaptive mechanism to water stress

Abstract Mesembryanthemum crystallinum plants exhibiting C3 pathway of photosynthesis were subjected for 3 weeks to nutrient solution of low temperature (10°) in order to reduce the absorption of water. By this stress treatment plant growth was largely retarded and Crassulacean Acid Metabolism (CAM) of photosynthesis was induced.

Mineral Ion composition and occurrence of CAM-like diurnal malate fluctuations in plants of coastal and desert habitats of israel and the Sinai

Summary1.The mineral ion composition and the occurrence of CAM-like diurnal malate fluctuations in species from 6 field locations in Israel and the Sinai were studied during the spring of 1974. The sites were a) a salt swamp near Acre on the Mediterranean Sea shore in the northern part of Israel, b) the high coast near Tel Aviv, c) the southern Dead Sea area near Sedom, d) the Negev highlands surrounding the ancient town of Avdat, e) the Wadi Paran in the southern Negev desert, and f) the Red Sea shore near the southeastern tip of the Sinai peninsula close to the Bedouin village of Nabek. The carbon assimilatory organs of the plants were analysed for Na+, K+, Cl− and SO42- as well as for malate at dawn and dusk.2.Most species analysed are characterized by high levels of mineral ions (mainly Na+/and Cl−) often exceeding 300–400 μeq per g fresh weight, and by high Na+/K+ ratios in their tissues mainly ranging from 10 to 20. These typical halophytic attributes are particularly found in species of the Acre salt swamp, of the Dead Sea area and the Red Sea shore and in many species of the Negev highlands.3.In plants occupying the Tel Aviv high coast habitats Na+ and Cl− are lower averaging 100 to 200 μeq per g fresh weight. The Na+/K+ ratio is about 5.4.Numerous species mainly inhabiting the less saline loessial plains and wadis of the Negev desert contain only up to 100 μeq Na+ and Cl− per g fresh weight and are characterized by Na+/K+ ratios of about 1 and below.5.The salt-accumulating species of the coastal habitats contain Na+ and Cl− in more or less equivalent amounts, i.e. halophytes of the “chloride type” in the terminology of Walter dominate these sites. In contrast, many inland halophytes chiefly belonging to the Chenopodiaceae accumulate much more Na+ than Cl− and/or SO42-.6.The special feature of Na+ contents which far exceed the sum of Cl− and SO42- distinguishes the inland Chenopodiaceae as a “physiotype” from members of other taxa. The Zygophyllaceae included in this study form a further “physiotype” which is characterized by higher Cl− than Na+ concentrations.7.Five species of the Aizoaceae family investigated showed no special pattern of mineral ion content.8.Certain species, especially some belonging to the Brassicaceae, showed a slight malate accumulation during the day.9.CAM-like diurnal malate fluctuations were only observed in four species: the halophytic Aizoaceae Mesembryanthemum crystallinum, M. forsskalii and M. nodiflorum and the non-halophytic Asclepiadaceae Caralluma It is suggested that, among halophytes, the capability to perform CAM is generally restricted to members of the Aizoaceae.

NaCl-induzierter Crassulaceensäurestoffwechsel bei einer weiteren Aizoacee: Carpobrotus edulis

Carpobrotus edulis grown for 24 days in nutrient solution plus 400 mM of NaCl shows the typical CO2 gas exchange reactions observed in CAM plants. Control plants grown in nutrient solution alone exhibit CO2 gas exchange reactions typical for C3 plants.SummaryCarpobrotus edulis grown for 24 days in nutrient solution plus 400 mM of NaCl shows the typical CO2 gas exchange reactions observed in CAM plants. Control plants grown in nutrient solution alone exhibit CO2 gas exchange reactions typical for C3 plants.

Carbon Assimilation Pathways in Mesembryanthemum nodiflorum L. under Natural Conditions

Summary During the spring of 1977, pathways of carbon assimilation were studied in specimens from natural populations of the annual Mesembryantbemum nodiflorum (Aizoaceae) occupying two sites in Israel: a) a coastal habitat at the Mediterranean Sea shore, and b) an inland habitat in the central Negev desert. Determinations of diurnal malate content and γ13 C values of the leaves indicated a shift in the mode of carbon assimilation during the life cycle of the plants. The data suggest the operation of C 3 photosynthesis in the plants during the wet season followed by the development of Crassulacean Acid Metabolism when rainfall ceases and water availability is reduced.

Einfluß von Wasserstreß auf die Aktivität der Phosphoenolpyruvat-Carboxylase bei Mesembryanthemum crystallinum (L.)

Four-and-a-half-week-old plants of Mesembryanthemum crystallinum (L.) were transferred to cooled nutrient solution or to nutrient solution of low oxygen content. These stress treatments are known to reduce the absorption of water by plants. Examination of the second foliar leaves showed that the stress treatments result in a malate accumulation in the leaf mesophyll during the night which is paralleled by a drastically increased activity of phosphoenolpyruvate carboxylase. The results are discussed in relation to alterations of leaf growth, leaf water content and leaf water saturation deficit of the plants treated as described.SummaryFour-and-a-half-week-old plants of Mesembryanthemum crystallinum (L.) were transferred to cooled nutrient solution or to nutrient solution of low oxygen content. These stress treatments are known to reduce the absorption of water by plants. Examination of the second foliar leaves showed that the stress treatments result in a malate accumulation in the leaf mesophyll during the night which is paralleled by a drastically increased activity of phosphoenolpyruvate carboxylase. The results are discussed in relation to alterations of leaf growth, leaf water content and leaf water saturation deficit of the plants treated as described.